Sensitivity to T-type Ca2+ channel antagonist correlates with the critical period. A, Examples of putative T-type Ca2+ spikelets (arrows) in 4w and 6w abGCs from perforated patch recordings. The spikelet reaches threshold for a Na+ action potential in the 6w abGC. Multiple Fisher's exact tests, 4w versus M p = 0.02. Total number of cells as indicated. B, Typical firing patterns in whole-cell recordings, with action potential bursts indicated by lines. Multiple Fisher's exact tests. 4w versus 8w and M p = 0.003, 6w versus M p = 0.04. C, Left, Percent of cells in TTA with bursts. Multiple Fisher's exact tests, not significant. Middle, Example firing patterns with first spike ISIs indicated in control (left) and TTA (right). Right, ISI in ACSF (circles) and TTA (triangles). Dotted line indicates ISI of 15 ms. Two-way RM ANOVA main effect cell age, F(3,26) = 3.0, p = 0.048; main effect TTA, F(1,26) = 27, p < 0.0001; interaction effect, F(3,26) = 9.06, p = 0.0003; Bonferroni's multiple comparisons, 4w p = 0.004, 6w p < 0.0001. D, The ISI in TTA relative to the ISI in ACSF (dotted line). One-way ANOVA F(3,26) = 9.2 p = 0.0002; Tukey's post hoc comparison, 4w versus 8w p = 0.04, 6w versus 8w p = 0.0008, 6w versus M p = 0.002. 4w, n = 8; 6w, n = 10; 8w, n = 7; M, n = 5.
